The pigment deposition such as pigmented spots and freckles on the skin is caused by the acceleration of melanin production, which is triggered by hormonal abnormality or ultraviolet stimulation, in the epidermal pigment cells and the excessive melanin deposition in the epidermis.
In order to prevent and improve such abnormal deposition of melanin pigment, a whitening agent is blended in external preparations for skin. Many of the whitening agents contain a compound having a melanin production inhibitory action as the active component.
Thus far, many studies have been carried out concerning the compounds having a whitening effect. For example, the in Patent Literatures 1 to 5, it is described that 4-alkylresorcinols have a whitening effect.
However, they have not been satisfactory in effect, safety, and stability.